The viewing angle of objectives lies between 5.degree. and 180.degree. with the last-mentioned objective belonging to the so-called fish-eye lenses. However, all of these objectives have in common that one has no influence on the outer boundary surface (which cannot be configured so as to be planar) and with which quality reductions in the edge regions and distortions are unpreventable especially for large viewing angles. These limitations with respect to the outer geometric form and also with respect to the imaging quality are, however, unacceptable for specific applications. A wide-angle view is often needed for observation and control tasks wherein quality reduction cannot always be permitted within various regions.
German Patent No. 2,031,971 discloses an arrangement for viewing a large air space by means of an arrangement of objectives having a facet-like configuration and connected in a honeycomb-like manner. These objectives cause the arrangement to have an uneven outer boundary surface and set a minimum size for the arrangement below which the latter cannot be built.
Published German patent application DE-OS 3,106,539 discloses a lens strip for copier apparatus wherein a prism is mounted behind each lens. In this way, a planar outer limiting surface for the entry of rays is not realizable and also the desired wide-angle view is especially not realizable.
German patent publication DE-OS 3,137,733 discloses an IR viewing device for providing a panoramic view but where the entire apparatus is rotated. In contrast thereto, German patent publication DE-OS 3,513,672 describes a 360.degree. viewing system wherein a mirror is needed in order to prevent blind angles.
A viewing head for periscopes is described in German patent No. 977,796 wherein a hemisphere is assembled from a plurality of plane-parallel plates.
European Patent No. 0,103,301 discloses an optical wide-angle arrangement having a horizontal viewing angle of 360.degree.. In this arrangement, an annular reflecting prism is utilized by means of which the incident radiation is mirrored on an objective. With this arrangement, it is possible to realize a 360.degree. panoramic view in a small solid-angle section with a planar outer limiting surface. The utilization of an optical annular lens for magnifying the solid-angle section, however, again leads to a non-planar outer limiting surface of the viewing window. In addition, the arrangement does not permit assembling a plurality of annular reflecting prisms to magnify the viewable solid-angle section.
The disadvantage of the state of the art is seen in that a large solid-angle region for a viewing window having a planar or smooth outer surface cannot be realized and/or reductions in quality and distortions in the peripheral regions cannot be prevented without providing for a movement of the window.